Stabilized thermoplastic cellulose ether composition



- tremely .-low temperatures are desirable. ever, when subjected .toelevated temperatures,

products. Icosity, strength, and flexibility also. result .fromprolongedstorage :or'exposure to ultraviolet-light and weathering. Theproblem of stabilization Patented Dec. 26, 1950 NTTED STATES PATENTOFFICE STABILIZED THERMQPLA-STIC CELLULOSE ETHEB-TCOMPOSITION WilliamKoch, Wilmington, DeL, and George .H. Pyle, Hopewell, 1 a". assignorstoIHercu'les Powtder flompany, Wilmington, "Del a corporation ofDelaware -NofDrawing. -ApplicationSeptember 25 1948, SerialNo. 51,322

"10 -Claims.

' This invention relates to the stabilization .of cellulose ethers and,more particularly, to the production of cellulose ethers and theircompositions which retain their vviscosityand gooolcolor during andafterexposure toheat, .light,.oxida- 'tion, Weathering andother degradinginfluences.

Cellulose ether compositions and -;particularly ethyl cellulosecompositions have .foundlconsiderable usefulness where .the propertiesof toughness, dimensional stability .and flexibility ,at ex-Howprolonged exposure-to .ultravioletlight oraging. in

' general, there "has been a discoloration and/or viscosity degradationwhichhas limited their usefulness to a considerable extent. Thus,compositions depositing a colorless mass from solu tion have given.relatively dark amber masses much like ftor'toise shell upon beingmolded at temperaturesof'the order of ZOO-300 C. In ad- ..dition,therehas been considerable loss of viscosity,'i. e., degradation,'leadlng'tobrlttle molded Similar discoloration .and :loss "of vislsparticularly diiiicult where relatively high heats are required, as infast molding, 'orwhen the material is exposed for prolonged periods :tosevere weatheringiconditrons.

In the past, viscosity stabilization has been efiected tosome-extentbythe-additionof certain amines and certain phenolic bodies.in most cases these have tended to "add color-themselves or havecontributed to atheformation of color in the cellulose ether. In the fewcases where color development has been less than that obtained wherenostabilizers were'used, the extent of color improvement has beeninsufficient'and hasbeenobtained llargelyundermoderate, rather thanhigh,lheat;conditions.

Some attempts have been made to improve color by treatment withbleaching agents and by treatmentwitnacids. where suchimprovementsin'color have been retained in the molding cperatlon, "they haveresulted in *such extreme loss of viscosity that a relatively uselessmolded product results. "Even mildly "l'ileaching,v slightly acidicmolded ethyl cellulose articles in pale or pastel shades. itEthylcellulose ,Inolded articles have. therefore,been made onlyin pigmentedor .dark colors.

Now, in accordance with this invention, it has been found.thatethylcellulose and other-thermoplastic cellulose ethers and :theircompositions may be effectively stabilized against :discoloration andviscosity degradation, when exposed to heat and weathering, by adding toor incorporating-with the cellulose ether a small amount ofdi-ter't-iamylphenol, alone or in combination with a sulfurdioxideproducing compound. used alone, the di-terteamylphenol exertsa.very definite stabilizing effect ion cellulose ethers and theircompositions, protecting .them .from .discoloration and degradation whenexposed .toheat, light, .air, weathering .and other degrading;iniluences. Optimum results .are obtained, however, 'when the.di-tert-amylphenol [used .in combination with small .amounts of a.sulfur .dioxide-producingcompound. Thus, in accordance with .thisinvention, cellulose vethers and their compositions may be molded-atelevated temperatures such as 200 C. and .above to form tough, shapedarticles very greatly improved in color after molding as compared withprevious molded compositions of this nature. As a result it is nowpossible to successfully prepare clear, relatively colorless moldingsand moldings in light and pastel shades.

-In-viewof the acidic nature of sulfur dioxide and in view of the factthat phenolic bodies are,

'in general, of an acidic rather than basic nature,

it is surprising and unexpected that the use of ditert-amylphenol aloneor in combination with sulfur dioxide in cellulose ether compositions atmolding temperatures brings about formation of tough, "undegradedproducts of improved color.

"Heretofore, it has been the experience in this field thatacids causedsevere degradation, sometimes accompanied by discoloration, whencellulose preparation .of molded articles therefrom which follow. Allparts and percentages given are by weight.

When.

EXAMPLE 1 Ethyl cellulose having 46.8% to 48.5% ethoxyl content and 100cps. viscosity was dissolved in 80:20 toluenezalcohol. Di tertamylphenol was added to a portion of the solution to give a compositioncontaining 1% di-tert-amylphenol, based on the weight of the ethylcellulose. The di-tert-amylphenol used in this example, and in all ofthe succeeding examples has the tertiary amyl groups substituted in theortho and para positions relative to the hydroxyl group. Films about 3mil in thickness were then cast from the composition, and portions ofthe films thus formed were heated for 48 hours at 120 C. in air. Filmsof the ethyl cellulose containing no stabilizer were also heated underthe same conditions. Viscosities of the samples before and after heattreatment were determined and from these figures the viscosity retentionwa obtained. Flexibility and discoloration were also noted. Table Ibelow compares the results obtained with the stabilized and unstabilizedethyl cellulose.

v TABLE I Evaluation of di-tert-amylphenol as stabilizer for ethylcellulose after heating for 48 hours at 120 C. in air Per Cent SampleFlexibility Discoloration fii gi f tion Unstabilized Flexible VerySlight. 27.3 di-tert-Anylphenol (1%) "do Nil 59.5

to ultra-violet light in a Fade-Ometer machine for 50 hours.Flexibility, discoloration and per cent viscosity retention weredetermined as before and are set forth in Table II below.

Parts Ethyl cellulose (44.5 to 45.5%

ethoxyl, 100 cps. viscosity) 85 Dibutyl phthalate Similar compositionswere prepared and molded containing (1) 2% di-tert-amylphenol, (2) 0.3%butadiene sulfone, and (3) 2% di-tertamylphenol and 0.3% butadienesulfone.

All samples were exposed to the 8-1 sun lampfog box cycle (2 hours inthe fog chamber, 2 hours irradiation under the 8-1 lamp, 2 hours in thefog chamber, 18 hour irradiation) for 120 hours. Color of discs aftermolding and color and condition of discs after exposure to S-l sunlamp-fog box cycle were determined and are set forth in Tables III andIV below. Colors were measured on the spectrophotometer, and values areexpressed as luminous transmittance and as the red trichromaticcoefiicient. The former value represents the amount of light that eachdisc will transmit, and the red coefiicient represents the per cent ofred in the total color value of the sample.

TABLE III Trichromatic 00- efficient (Red) Luminous Transmittance, PerCent Sample Unstabilized .i 2% di-tcrt-Amylphenol 0.3% Butadicne sulioner' 2% di-tert-Amylphenol and 0.3% butadienc sulione TABLE IV Color andcondition of discs after exposure to 8-1 sun lamp-fog box cycle(spectrophotometer color values) Luminous 'lrichro- Sample TransmitmaticCondition tance, Per Coefli- Cent cient (Red) Unstabilized 1. l) .6017Surface badly crystallized and I disintegrating. 2% d1 tart-amylphenol21. 6 .4365 Fine surface craze. 0.3%Butadicnc sulfone 14.8 .4962 Surfacebadly crystallized and disintegrating. 2% di-tert-Amylphenol and 22.0.4307 Fine surface craze.

0.3% Butadiene sulfone.

. I TABLE II Evaluation of di-tert-amylphenol as stabilizer for ethylcellulose after exposure in the Fade- Ometer for hours Per Cent SampleFlexibility Discoloration g if tion Unstabilizeiu; Brittle Nil 5.4dl-tert-Amylphenol (1%). Flexible..." Nil 40.7

lateness Xhox cycle. Furthermore, the surface condition or ethylcellulose plastic .disc containing a small .amount :of.di-xert-amylphenol :alone or in comrhinetion 'with butadiene sulfonewas in .much bettter condition than either the unstabilized :ethylcellulose sdisc or :the ethyl cellulose disc acontaining butadienessulfone :alone. 'The surmice of the ethyl cellulose :discs which .didnot contain any di-tert-amylphenol was badly crystallized:andcdis'integrating in contrast to a ffiue crazing without surfacedisintegration aor crystallization for the ethyl cellulose discs :con-

.teining'za small amount of v di-tert-amylphenol.

EXAMPLEB .Io 1'15 .grams of flake .ethylcellulose contain .ing 9.35% byweight of butadiene sulfone was .added 62,,grams of dihutyl phthalateand7 grams :of di- -tert-amylphenol, and .the mixture was placed .on atwo-roll .mill with the .rolls at 3101t-l0 With .the .mill running, anadditional '175grams of the same flake ethyl-cellulose wasadded and thematerial was milled at 300 -.to 132.0 for minutes. The composition was:then stripped from the rolls as a well-colloided plasticshefit, brokeninto pieces, and ground to about .8 mesh with an Abb cutter, Exactly 200grams of this molding powder was placed in a glass-top Quartiar with.the top inplace butnot sealed. The .jar .and its contents were heatedI01 16 hours at 100 C. in an .oven. From this molding powder a.plastic'disc 2% .inches in dimaster and 0.065 inch thick wascompression molded .in a conventional ring and plug mold,

employing "5 gramsof molding powder and moldingat 20001112. p. s. i.at200 clfors minutes.

.A. similar molding .powder and molded disc were prepared by the sameprocedure from the same flake ethyl cellulose but without any.diter't-am-ylphenol.

Viscosity measurements were then made on the original .flake ethylcellulose, on ithemolded .disc

or ethyl cellulose plastic composition containing di-Ltart-amylbhenoland .on the molded disc of ethyl cellulose plastic composition withoutthe .di-itert-amylphenol. Viscosity values for the "molded plasticcompositions were corrected .for' jplasticizer content in order to placeall viscosities on a comparable basis with the viscosity of'th'exolfiglnal flake ethyl cellulose as the reference standard.

"Viscosities were measuredat.25'C.:L-0;1' C. on i5'%'b,y WeightSolutions of the original flake ethyl cellulose and of :the moldedplastic compositions in a solvent composed of '80 parts toluene and '20parts denatured ethyl alcoholby weight. Viscosit'y values are given'inTable V below.

TABLE V Evaluation of di-ztert-amylphenol as stabilizer for ethylcellulose after high temperature milling and moldinpopenations 146.4%cthoxyl content.

.These :data :illustrate that .a small amount of :di-tert-amylphenol inan ethyl cellulose iplastlc composition which is subjected .to hightemper- .ature milling and molding operations effectively stabilizes:the ethyl cellulose with respect :to "vis- .cosity retention.

The method and icompositions of this invention call for use of celluloseethersof the thermo- .:plastic'type1and of suflicient'degree ofpolymerization .to, yield tough, moldedarticles. Ingeneral. cellulose.ethers soluble in any of the common organic solvents, :such 22.5acetone, benzene, toluene-alcohol, methanol, ethanol, .ethyl'acetate,butyl :acetate, :and the like, are of the required thermoplastic type.Ethyl i-"cellulose having :an ethoxyl content between about 37% andabout 52%, preferabl between about 43% and about 1.48% :and .having *aviscosity .;of "at least about 20 cps, is particularly suitable.However, thermoplastic propyl cellulose, ethyl .propyl cellulose, ethylbutyl cellulose, methyl ethyl cellulose, .and benzyl cellulose arelikewise useful in molding compositions, and, like ethyl cellulose,"their molding compositions are very greatly improved ;in .color'jof themolded product by proceeding in accordance with .this invention. .It isdesirable that the cellulose ether-s be so prepared or purified as v.toeliminate .any substantial proportion of free acid. Thus, treatment withstrong acids should :be avoided unless there is subsequentneutralization of any free acid groups by basic ions, such as sodium,calcium, magnesium, cesium, copper, and the like.

The stabilizers according -.to .the present .invention .may beincorporated before, during :or after preparation of the cellulose ethercompositions or while the cellulose ether compositions .are .being"molded or otherwise formed into finishedplastic articles. For example,.when di- -tert-amylphenolaloneis used, the cellulose ether may bedissolved .in a suitable solvent to which the di-tert-amylphenol isadded, after which solvent is removed. Alternatively, the celluloseether maybe suspendedin water or a swelling medium, such as aqueousalcohol and a solution of the stabilizer added to the suspension forabsorption by :the cellulose ether. Again the stabilizer may be addedduring a tumbling, stirring, =or othersimilar operation for distributingthe stabilizer'through the granular cellulose ether. Incorporation ofthe stabilizer at some stage of manufacture .is desirable, since itfrequently happens that the cellulose ether .is stored for considerableperiods before use, and the presence of an-efiective stabilizer preventsany substantial degradation due to aging.

The stabilizer may also be incorporated during preparation of theproduct in which the cellulose ether is eventually employed. Forexample, in the preparation of cellulose-ether lacquers, moldingpowders, 'etc., the stabilizer may be added to the finished lacquer orto the lacquer solvent during or prior to dissolving the other lacqueringredients; to the mixture of ingredients prior to or during formationof a molding powder, etc.

The amount of di-tert-amylphenol utilized may varyfrom about 0.5% 'toabout 5.0% of the weight of the cellulose ether. Preferably, it isemployed in amounts between about 1% and about 3%, 1% usually being theoptimum quantity to obtain satisfactory stability and other requiredcharacteristics. Larger amounts than about 5% produce no substantialadditional stabilizing effeet, while amounts below'about 0.5% usually do'75 not create the desired degree of stabilization.

7 When sulfur dioxide is included substantially similar amounts ofdi-tert-amylphenol will be utilized in order to obtain maximum stabilitycharacteristics. Sulfur dioxide may be provided as such at the time ofmolding the cellulose ether composition containing thedi-tert-amylphenol, by passing a small stream of sulfur dioxide into themolding chamber or into a chamber or hopper by which the thermoplasticcomposition is led to the molding chamber. A similar result is ob- :2

tained by subjecting a molding powder of the cellulose ether compositionto an atmosphere of sulfur dioxide, whereb it absorbs some of the sulfurdioxide, and then molding the composition by compression, injection, orextrusion under heat before the absorbed sulfur dioxide has been lost.

Usually it is more convenient to incorporate in the molding compositiona compound which will decompose at the molding temperature to formsulfur dioxide, and di-tert-amylphenol, and then molding the compositionunder heat. Temperatures utilized in molding will be at least sufiicientto cause release of sulfur dioxide from the particular compound used.Generally these will be of the order of about 200 0., althoughtemperatures above or beiow this figure may be used. By this method, asmall amount of sulfur dioxide is released under the heat of the moldingoperation. Thus, there is provided a thermoplastic cellulose ethermolding composition containing both the compound capable of releasingsulfur dioxide and the di-tert-amylphenol. Such a composition is capableof being molded to strong, tough articles which may be of pale color ora pastel shade or of very greatly reduced color in the case of cleararticles.

The sulfur dioxide-releasing compound may be incorporated in thecellulose ether at the time it is manufactured, or it may beincorporated during the preparation of the molding composition. Eitherof the latter procedures has the advantage of providing the celluloseether with a color protective influence during the milling needed toform a molding powder.

Any compound which is substantially colorless,

which does not discolor under heat, and which does not in itselffunction as an acid stronger than sulfurous acid is suitable. Thesulfones of aliphatic compounds, such as those derived from butadiene,piperylene, isoprene, 2-methyl pentadiene, amyldiene, or other dienehydrocarbons, are particularly useful since they release sulfur dioxidefreely at 200 C. without leaving any appreciable residue. Polyproplyenesulfone, polyalkyl-polysulfones generally, and cyclic dipro-' octylsuccinate, sodium sulfodilauryl succinate,

equivalent potassium compounds, and similar derivatives of substitutedsuccinates, have been found particularly suitable since the residue isquite compatible in the cellulose ether compositions and, in fact,functions as a plasticizer. These compounds may be prepared bycondensation of sodium bisulfite with the corresponding esters of maleicacid. Any aliphatic or alicyclic sulfonate which will release sulfurdioxide upon heating is suitable. Alkyl and other organic sulfltes, forexample, dimethyl sulfite, diethyl 301-;

fite, dibutyl sulfite, methyl bisulfite, ethyl bisulfite, acetonebisulfite, normal-heptaldehyde blsulfite, and sodium formaldehydesulfoxylate, were found to function by release of sulfur dioxide at 200C. Inorganic compounds, such as sodium bisulfite, sodium meta-bisulfite,potassium bisulfite, calcium bisulfite, sodium hydrosulfite, and thelike, which are capable of releasing'sulfur dioxide upon heating at 200C. have also been found suitable. The inorganic materials are of use inpale pigmented molding compositions but tend to add haze to compositionsintended fo clear moldings.

The quantity of sulfur dioxide or sulfur dioxide-releasing materialwill, in general, be quite small but may vary considerably with theparticular compound utilized. It is most easily expressed on the basisof the content of sulfur dioxide in free or combined form, and, on thisbasis, at least about 0.005% by weight of sulfur dioxide based upon thecellulose ether in the molding composition should be present during themolding operation in order to obtain improvement in color of the moldedarticle. Preferably, a quantity between about 0.05% and about 0.5% ofsulfur dioxide based on the weight of the cellulose ether will beutilized, it being understood that this amount represents only thesulfur dioxide content of the actual compound present. In general, nomore than about 0.2% of sulfur dioxide in loosely combined form need bepresent, and in view of the possibility of corrosion of equipment bysulfur dioxide, no more than this amount will ordinarily be used. In anycase, no more than 2% of combined or free sulfur dioxide should be usedbecause of development of objectionable odor and degradation, scorching,etc. in the finished plastic.

Where gaseous sulfur dioxide is used, only a small amount need be passedthrough the mold ing composition as absorption of only very smallamounts is needed. Where butadiene sulfone is used, 0.2 to 0.5% on theweight of the cellulose ether (equivalent to 0.11% to 0.27% sulfurdioxide) is an optimum quantity, some of the sulfur dioxide beingreleased in milling to form molding powder and the remainder, or some ofthe remainder being released in molding. However, 0.01% to 2.0% of thesulfone, based on the cellulose ether, may be used. When sodiumsulfodioctyl succinate or homologous compound is used, 0.3% to 1.0% ofthe compound is optimum, although 0.05% to 4.0% may be used. (Thisrepresents 0.005% to 0.29% sulfur dioxide based on the cellulose ether.).The amount may be less than in the case of butadiene sulfone, asindicated by the figures, because there is less sulfur dioxide releasedin milling to form molding powder, and, therefore, relatively moresulfur dioxide available in the molding operation. It will beappreciated that, depending on particular compounds, compositions, anduses, the optimum quantities will vary considerably.'

It will be understood that plasticizers, such as dibutyl phthalate,diethyl phathalate, butyl stearate, triphenyl phosphate, tricresylphosphate, raw castor oil, nonvolatile mineral oils, methyl phthalylethyl glycolate, hydrogenated methyl abietate, and the like, may beincorpoasra rulee. these substances; are; not used;

the like; Temperatures may vary from 100 to 300- C2. The invention isparticularly valuable in permitting molding atthe relatively high butefllcient and frequently necessary temperatures.

It will be appreciated that the compositions:

in accordance with this invention are also; useful where heat isnotessential for shaping but where a. composition may be subjected torelatively high temperatures or to moderately high temperatures for longperiods of time. Thus, the: compositions retaingood color and stabilityover long periods of exposure toheat and light a in the form of lacquerfilms, electrical insulation, impregnated and coated fabric, and in filmor sheeting.

It has been found that the compositions in accordance with thisinvention can be molded at" quite high temperatures without theformation of rather dark coloras normally encountered with celluloseethers; The compositions are also stabilized against degradation in theform of severe viscosity drop; Stability of this nature preservestoughness. Furthermore, the compositions are capable of" withstanding.ultraviolet'light" of 'the type encountered in exposure to sunlight andsun lamps'forlong periods without developmentlof darkspots,discoloration, and other. degradation. The invention permits. thepreparation of clear and pastel shades in thermally molded celluloseether compositions.

'Viscosities given throughout this specification. are defined in termsof'centipoises as determined on 5% solutions of the cellulose ether in80:20 toluene:alcohol at 25 C. The per cent viscosity retentions werecalculated by determining the viscosities of a given sample :before andafter treatment, such as heat-treatment, and dividing the latter by theformer.

The S-l sun lamp-fog box cycle is fully described in the Governmentpublication dated January 24, 1944, and entitled Federal Specificationfor Plastics, 'Org-anic-General SpecificationsTest Methods under testLP406a. The cycle includes exposure in a fog chamber for two hours, twohours irradiation under an S-l lamp, two hours additional exposure inthe fog chamber, followed by eighteen hours irradiation. The

cycle may be repeated any number of times.

What we claim and desire to protect by Letters Patent is:

l. A stabilized cellulose ether composition comprising a thermoplasticcellulose ether and from about 0.5% to about 5% of di-tert-amylphenolhaving the tertiary amyl groups substituted in the ortho and parapositions relative to the hydroxyl group, said composition beingstabilized with respect to viscosity and color during and after exposureto heat, light, oxidation, and weathering by virtue of the presencetherein of said di-tert-amylphenol.

2:, A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose and from accused about-015% toabout 5% ,ofdi;-tert-amylphenol= having the tertiary amyl groups substituted in;v

the ortho and-v para: positions relative. to the hy: droxyl group, saidcomposition being stabilized.

' with respect to viscosity and color during and.

after exposure to: heat, light, oxidation, and" weathering by virtue ofthe. presence-therein. of said di-tert-amylphenol.

3. Astabilizedzcellulosez ether composition coma prising athermoplasticcellulose ether; a sulfur. dioxideproducing.- compound which. is.substan; tially colorless, which does not: discolor under heat, whichdoesn'ct in itself function. asaan acid? stronger than: sulfurous' acidand which releasessulfur dioxide at 200 in an amount atileast about0.005% and-not morethani2=% of theweight of the cellulose ether onthebasis of: thecontent of combined sulfur dioxide, and from about 0.5%to about 5% of di-tertsamylphenol? having: the: tertiary amyl groupssubstituted in the ortho. and para positions relative to the hydroxylgroup, said composition being stabilized. with respect to. viscosity andcolor during and after exposure: to:-

heat, light, oxidation, and weathering by virtue:

stronger than sulfurous acid and which releases;

sulfur dioxide. at 200 C., in an amountbetween about 0.005% and about0.5% oftheweightvofi the cellulose ether on the basi's-of the content ofcombined'sulfur dioxide; and from about 0.5 to about 5% ofdi-tert-amylpheno1 having the tertiary amyl groups substituted in theorth'oand para positions relativeto 'thehydrcxyl group, said compositionbeing stabilized with respect to viscosity and color during and afterexposure to heat, light, oxidation, and Weatheringby'virtue of thepresence therein of said di-tert-arnyl' phenol and" said sulfur dioxiderel'easing compound.

5. A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose, an allphatic diene sulfone which is substantiallycolorless, which does not discolor under heat, which does not in itselffunction as an acid stronger than sulfurous acid and which releasessulfur dioxide at 200 C., in an amount between about 0.005% and about0.5% of the weight of the ethyl cellulose on the basis of the content ofcombined sulfur dioxide, and from about 0.5% to about 5% ofdi-tert-amylphenol having the tertiary amyl groups substituted in theortho and para positions relative to the hydroxyl group, saidcomposition being stabilized with respect to viscosity and color duringand after exposure to heat, light, oxidation. and weathering by virtueof the presence therein of said di-tert-amylphenol and said sulfurdioxide-releasing compound.

6. A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose, butadiene sulfone in an amount between about 0.01% andabout 2.0% of the weight of the ethyl cellulose, and from about 0.5% toabout 5% of di-tertamylphenol having the tertiary amyl groupssubstituted in the ortho and para positions relative to the hydroxylgroup, said composition being stabilized with respect to viscosity andcolor durin and after exposure to heat, light, oxidation, and weatheringby virtue of the presencelthereln I ll of said di 'tert-amylphenol andsaid butadiene sulfone.

7." A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose, a sulfodialkyl succinate which issubstantiallycolorless, which does not discolor under heat, which doesnotin itself function as an acid stronger than sulfurous acid and whichreleases sulfur dioxide at 200 C., in an amount between about 0.005% andabout 0.29% of the weight of the ethyl cellulose on the basis of thecontent of combined sulfur dioxide, and from about 0.5 to about ofditert-amylphenol having the tertiary amyl groups substituted in theortho and para positions relative to the hydroxyl group, saidcomposition being stabilized with respect to viscosity and color duringand after exposure to heat, light, oxidation, and weathering by virtueof the presence therein of said di-tert-amylphenol and said sulfurdioxide-releasing compound.-

8. A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose, sodium sulfodioctyl succinate in an amount betweenabout 0.05% and about .0% of the weight of the ethyl cellulose, and fromabout 0.5% to about 5% of di-tert-amylphenol having the tertiary amylgroups substituted in the ortho and para positions relative to thehydroxyl group, said composition beingstabilized with respect toviscosity and color during and after exposure to heat, light, oxidation,and weathering by virtue of the presence therein of saiddi-teit-amylphenol and said sodium sulfodioctyl succinate.

9. A stabilized cellulose ether composition co 1.- prising athermoplastic ethyl cellulose, an organic sulfite which is substantiallycolorless, which does not discolor under heat, which does not in itselffunction as an acid stronger than sulfurous acid and which releasessulfur dioxide at 200 C., in an amount between about 0.005% and about0.5% of the Weight of the ethyl cellulose on the basis of the content ofcombined sulfur dioxide, and from about 0.5% to about 5% ofdi-tert-amylphenol having the tertiary amyl groups substituted in theortho and para positions relative to the hydroxyl group, saidcomposition 12 being stabilized with respect to viscosity and colorduring and after exposure to heat, light, oxidation, and Weathering byvirtue of the presence therein of said di-tert-amylphenol and saidsulfur dioxide-releasing compound.

10. A stabilized cellulose ether composition comprising a thermoplasticethyl cellulose, diethyl sulfite in an amount between about 0.005% andabout 0.5% of the weight of the ethyl cellulose on the basis of thecontent of combined sulfur dioxide, and from about 0.5% to about 5% ofdi-tert-amylphenol having the tertiary amyl groups substituted in theortho and para positions relative to the hydroxyl group, said com-iposition being stabilized with respect to viscosity and color durin andafter exposure to heat, light, oxidation, and weathering by virtue ofthe pres ence therein of said di-tert-amylphenol and said diethylsulfite.

WILLIAM KOCH.

GEORGE H, PYLE.-

REFERENCES CITED The following references are of record in. the file ofthis patent:

UNITED STATES PATENTS Bacher et al., Rec. des Trav. Chim. des Pay- Bas(1935) DD. 538 to 544.

1. A STABILIZED CELLULOSE ETHER COMPOSITION COMPRISING A THERMOPLASTICCELLULOSE ETHER AND FROM ABOUT 0.5% TO ABOUT 5% OF DI-TERT-AMYLPHENOLHAVING THE TERTIARY AMYL GROUPS SUBSTITUTED IN THE ORTHO AND PARAPOSITIONS RELATIVE TO THE HYDROXYL GROUP, SAID COMPOSITION BEINGSTABILIZED WITH RESPEC TO VISCOSITY AND COLOR DURING AND AFTER EXPOSURETO HEAT, LIGHT, OXIDATION, AND WEATHERING BY VIRTUE OF THE PRESENCETHEREIN OF SAID DI-TERT-AMYLPHENOL.